Blood glucose monitoring is a way of testing the concentration of glucose in the blood (glycemia). It is important in the care of diabetes mellitus.
A blood glucose test is generally performed by piercing the skin (typically, on the finger tip) to draw blood, then placing the blood on a chemically active disposable strip which indicates the result either by changing colour, or changing an electrical characteristic, the latter being measured by an electronic meter.
Most people with Type 2 diabetes test at least once per day (usually before breakfast) to assess the effectiveness of their diet and exercise.
Many people with Type 2 diabetes use an oral medication to combat their insulin resistance, and test their blood glucose before and after breakfast to assess the effectiveness of their dosage. Diabetics who use insulin (all Type 1 diabetes patients and many Type 2 diabetes patients) usually test their blood sugar more often, such as 3 to 10 times per day, both to assess the effectiveness of their prior insulin dose and to help determining the time of their next insulin dose.
Improved technology for measuring blood glucose is rapidly changing the standards of care for all diabetic people. There are several methods of blood glucose testing currently available.
Chemical Test Strips: Chemical test strips are a medium cost method for monitoring blood glucose. A fairly large drop of blood, usually taken from the fingertip, is placed on a chemically prepared strip, called a blood glucose testing strip. The chemicals in the strip react with the blood, changing color according the concentration of glucose, which can then be read by comparing the color with a chart on the side of the test strip container.
Blood Glucose Meters: A blood glucose meter is an electronic device for measuring the blood glucose level. A relatively small drop of blood is placed on a disposable test strip which interfaces with a digital meter. Within several seconds, the level of blood glucose will be shown on the digital display. Sample sizes vary from 30 to 0.3 μl. Test times vary from 5 seconds to 2 minutes (modern meters are typically below 15 seconds).
Although more expensive, blood glucose meters seem a breakthrough in diabetes self care. As the drops of blood needed for the meter may be smaller, the pain associated with testing is reduced and the compliance of diabetic people to their testing regimens is improved. Although the cost of using blood glucose meters seems high; it is believed to be a cost benefit relative to the avoided medical costs of the complications of diabetes.
A recent and welcome advantage is the use of small blood drops for blood glucose testing from other places than the finger tips. This alternate site testing uses the same test strips and meter, is practically pain free, and gives the finger tips a needed break if they become sore.
A further improvement is provided by a continuous blood glucose monitor: A continuous blood glucose monitor (CGM) determines blood glucose levels on a continuous basis (every few minutes). A typical system consists of:                a) disposable glucose biosensor placed just under the skin, which is worn for a few days until replacement;        b) a link from the sensor to a non-implanted transmitter which communicates to a radio receiver;        c) an electronic receiver worn like a pager (or insulin pump) that displays blood glucose levels on a practically continuous manner, as well as monitors rising and falling trends in glycemic excursions.        
Continuous blood glucose monitors measure the glucose level of interstitial fluid. Continuous monitoring allows examination of how the blood glucose level reacts to insulin, exercise, food, and other factors. The additional data can be useful for setting correct insulin dosing ratios for food intake and correction of hyperglycemia. Monitoring during periods when blood glucose levels are not typically checked (e.g. overnight) can help to identify problems in insulin dosing (such as basal levels for insulin pump users or long-acting insulin levels for patients taking injections). Monitors may also be equipped with alarms to alert patients of hyperglycemia or hypoglycemia so that a patient can take corrective action(s) (after fingerstick testing, if necessary) even in cases where they do not feel symptoms of either condition.
Studies have demonstrated that patients with continuous sensors experience less hyperglycemia and also reduce their glycosylated hemoglobin levels. This technology is an important component in the effort to develop a closed-loop system connecting real-time automatic control of an insulin pump based on immediate blood glucose data from the sensor.